Mobile machines are known to include a power system for generating power. For example, a power system may include one or more electric motors, a generator unit, and a power-transfer system for transferring power from the generator unit to the one or more electric motors. It is known for the generator unit to include an engine for driving a generator. Often, the generator unit is housed within an enclosure to protect the generator unit from environmental elements. The enclosure is likely to trap a large amount of heat created by the generator unit, which may be dissipated via one or more cooling devices to maintain the generator unit operating conditions at an acceptable level. For example, it is known for a generator unit to include a radiator, a cooling fan, and/or other cooling devices for dissipating the heat within the enclosure.
In a generator unit mounted on a locomotive, it is known to house the generator unit within an enclosure and to cool the generator unit with one or more cooling devices. For example, it is known to employ a cooling passage located in walls of the enclosure. It is also known to circulate cooling air over the generator unit with a cooling fan.
Under some circumstances, locomotive power systems may discharge cooling air out of a top portion of the enclosure. For example, a portion of the power system enclosure may be covered with a wire mesh-type material. While the wire mesh-type material may allow cooling air to escape the enclosure and prevent large debris from entering the power system enclosure of the locomotive, environmental elements, such as precipitation (e.g., rain, snow, ice) and other debris, may penetrate the wire mesh-type material and contact the generator unit, thereby causing damage or otherwise reducing the life and efficiency of the generator unit.
One example of a roof structure providing ventilation is described in U.S. Pat. No. 4,609,126 to Janda (“the '126 patent”). The '126 patent discloses a venting cap for an enclosure used in an outdoor environment. The venting cap includes an inner roof panel and an outer roof panel. The outer roof panel includes a single outer aperture that is centrally positioned and offset from a plurality of inner apertures formed on the inner roof panel. Since the outer aperture is offset from the inner apertures, the venting cap may reduce the likelihood of precipitation passing through inner apertures into the apparatus housing. Further, an interior of the enclosure may be ventilated with cool air entering from an opening in the bottom of the enclosure and hot air may be vented through the outer aperture.
Although the venting cap of the '126 patent may alleviate some of the problems associated with cooling an enclosure, other problems may persist. The venting cap of '126 may not provide sufficient ventilation to remove heat generated by a power system, such as a locomotive power module. Additionally, the venting cap of the '126 patent may not be well suited for permitting operators to service the equipment housed within the enclosure by, for example, walking on the outer roof panel.